<!DOCTYPE html>
<script>
fetch('./large_image.png')
  .then(response => response.blob())
  .then(blob => {
    var reader = new FileReader();
    reader.onloadend = () => {
      download(reader.result);
    }
    reader.readAsDataURL(blob);
  });

function download(url) {
  var a = document.createElement("a");
  a.href = url;
  a.download = 'large.png';
  document.body.appendChild(a);
  a.click();
}
</script>

